Sintered powder metal mold



g- 7, 1963 R. w. CALLENDER ETAL 3, 01,514

SINTERED POWDER METAL MOLD Filed D80. 4, 1961 IN VENTOE$ gqL ox-z I/l/CALLEA/DEE A/QEOLQEE/EHL 477OENE United States Patent 3,101,514 SENTERED POWDER METAL MOLD Ralph W. Callender, Hinsdale, and Harold R. Eiehl, Lake Villa, llh, assignors to International Harvester Company, Chicago, lll., a corporation of New Jersey Filed Dec. 4, 1961, Ser. No. 157,871 3 Claims. (CI. 22-10) ing of cores, the said mold being of a permeable type so as to provide for the release of gases incident to the curing of the cores.

A still further object is the provision of an improved core box for producing cured shell mold cores, the said hlhlfili Patented Aug. 27, 1963 though not shown, a copper junction strip is connected to the rear of each of the mold sections 11. Negative leads or wires 15 are connected to the copper junction strips 14 as indicated at 16. Similarly, positive, leads or wires 17 are connected to the copper junction strips which are secured to the rear of the mold sections 11 As indicated in FIGURE 1, the mold 10 is suitably supported on an electrical insulating plate 18 which in turn is supported on a table 19.

A core blower 20 is mounted on the table 19, the said core blower 20 including a support 21 having a blowhead 22 which is connected to a conduit 23. The core blower 29 may be of conventional construction which is adapted to blow sand under high pressures through the blowhead 22 into the core mold 10 supported beneath the blowhead 22.

core box including improved provisions whereby the said cores may be cured immediately afiter the cores have been blown into the box.

A still further object is to provide an improved core box assembly particularly adapted for use in connection with blowing of shell mold cores wherein the cores consist of a resin-sand mixture which upon heating sets and forms a hardened core, the said core box being adapted to respond to an electnical current for heating the core box, thus setting the blown cores, immediately after a core blowing operation.

A still further object is the provision of an improved core box made of a sintered powdered metal material, the said box having a porous and permeable construction whereupon the box has a good electrical resistivity so that upon the application of an electrical current to the box, the box heats by resistance and therefore cores which are blown into the box are immediately cured after the blowing operation.

A still further object is the provision of an improved process of constructing a powdered metal core box.

Another object is to provide an improved core box constructed of a sintered metal powder, said box having a porous permeable character including particles of copper infiltrated throughout to provide increased strength.

These and further objects wil become more readily apparent from a reading of the description when examined in connection with the accompanying sheet of drawings.

In the drawing:

FIGURE 1 is a perspective view of an improved core box supported on a blowing machine for blowing shell mold cores; and

FIGURE 2 is a perspective view of a one-half of a core box assembly.

In FIGURE 1, a mold is generally designated by the portion reference character 10. The mold 10 comprises a pair of mold sections or half molds 11, one of said half molds 11 being shown in FIGURE 2. Each mold section 11 comprises a parting face 12 having a plurality of recesses or cavities 13. The mold sections 11 are unique in that they are manufactured from metal powder, which may be iron, suitably sintered by conventional powdered metal sintering methods. In addition the mold section 11 includes a generally porous structure which gives the mold a high permeability; In the art of powder metallurgy the porosity of the sintered powder metal is conventional. This porosity is particularly advantageous and unique in a mold box or core mold.

As indicated, a copper junction strip 14 is connected at the forward ends of each mold section 11. Similarly,

The b'lowhead 22 may be suitably adjusted in a vertical direction and when the mold 10 is positioned in place the blowhead 22 may be supported over the upper ends of the mold sections 11 as indicated. The mold 10 is securely positioned on the table 19 and the blowhead 22 is securely fastened on top of an insulating plate 24 which electrically insulates the mold from the blowhead 22. The insulating plate 24 may be suitably apertured (not shown) so that the blowhead 22 may be free to blow sand into the mold 110.

A stationary clamp member 25 is positioned on one side of the table 19. A supporting rod 26 projects laterally from the stationary clamp member, 25 in the direction of the mold 10. As indicated in FIGURE 1, a movable clamp member is designated at 27. This clamp member 27 has conuectedjthereto a rod 28 which in turnis rigidly connected to a clamp plate 29. The clamp plate 29 engages an electricaljinsulating pad 30 which electrically insulates the movable clamp member 27 from the mold 10. The clamp member 27 is movable upon guide rails 31, the said clamp member including laterally spaced slots each of which straddles one of the guide rails 31. A clamping screw 33 extends through one side of the clamp member 27 and is adapted to engage one of the rails 31 to secure the said clamp member against longitudinal movement with respect to one of the guide rails 31. The rod 26 also has a suitable clamp plate which is adapted to engage an insulating pad similar to the pad 30, the latter pad and clamp plate not being shown in FIGURE 1.

Thus by positioning the mold sections It} in upright and adjacent contiguous position on the table 19 as indicated in FIGURE 1, the said mold sections 11 may be firmly secured together with their parting taces in contiguous relation by means of the movable clamping mechanism 27. In this position the recesses or cavities 13 are in complemental relation forming a plurality of cavities or mold chambers. Since the mold sections 11 are tightly held against each other, mold sand can be blown into the cavities through the blowhead 22 which is brought, tightly downwardly into engagement with the insulating plate 24. Thus the mold is now in position for receiving the core sand mixture.

The core sand mixture may. consist of a suitable resin and a fine sand which is mixed together in the same proportions as the well kno-wn shell mold mixtures. This sand resin mixture is then blown into the cavities formed by the complemental recesses 13.

The electrical wires 15 and 17 are suitably connected to a source of electrical energy where upon current flowing through the wires 17 the powdered metal mold 1.0 heats by resistance whereupon sufficient heat is generated to cure or bake the sand-resin mixture which has been blown into the cavities. This heatingefiectuates curing of the shell mold cores. Incident to the heating gases are liberated from the shell mold cores and these gases are tree to escape through the porous construction of the mold sections 11. Thus by virtue of the high permeability of the mold sections 11, the gases are easily liberated from the mold without any further action on the part of the operator.

' Thus it can be seen that the powdered metal mold is advantageous. in the core blowing operation and by virtue of the natural resistance of the mold to the electrical current, heating and curing of the sand cores can be accomplished without moving the mold to a separate turnace for heating. Thus a quick heating and curing operation occurs immediately after the blowing of the cores. iron, though other metal pcwdersresulting; in permeability and porosity may be utilized.

An example of the iron metal power composition utilized contained by weight is as. hollows:

Percent Fe total 98.8 H loss .30 C .04 SiO .10 S .007 P .010

The density of this powder was 2.35-2.45 .g./cc. flow (in Hall llow meter)30 seconds. I The sieve analysis of the powder with US. Tyler mesh was as follows:

In order to secure increased strength it is also desirable to include a certain quantity of copper powder, the copper being finely and widely dispersed throughout the sintered powder metal structure. Thus a copper powder can be intermingled with the mixture in the manufacture of the mold. This mixture not destroy the qualities of porosity and permeability.

The steps of making the powdered metal molds consists of shaping a pattern in the usual manner. The pattern may be shaped on a metal plate and in turn also may be constructed of metal. The pattern may be placed in a. suitable, flask or box and the metal powder may be The metal powder which is utilized may be of poured into the box over the pattern to completely cover the same. The metal powder used, as indicated abowe, may be iron or other similar powders. In addition, a porosity forming material may be included in the powder in order to volatilize during sintering whereby a desired degree of interlocking porosity is accomplished in the finished product. Further, a certain quantity of cooper powder may be utilized. The copper powder may be infiltrated into the material after sintering and a percentage by weight of 5% to 15% is utilized. After the powder mix- .ture is placed in the box over the pattern the box may then be placed in a sintering furnace and a sintering operation is completed. The sintering temperature was one hour at 1900 'F. After sintering the density of the mold was 2.63 g./cc. with-a porosity of 60%. After the box is removed from the :iurnace thepowder metal mold isthen removed, the pattern and the strips 14 may be applied. The electrical resistivity. is determined as follows:

The stable value of resistance tor a sintered iron bar 12.5 inches. longand. 1, sq. in. cross sectional area is 0.003988 ohm. By applying 180 amperes to the bar the temperature will level olf at about 550 F.

This temperature of the mold was considered ideal tor shell mold cores. Thus a powdered metal mold box sectioncan be quickly andeasily formed, the said assembledmold consisting of two of the sections, providing a complete mold, core, or pattern box having the desired Intercom municating p0r0sity.--That type of porosity in a sintered compact in which the pores are connected so that fluid may pass trom one to the other completely through the compact. The term is shortened simply to porosity in the claims.

Pore forming material.- A substance included in a powder mixture which volatilizes during sintering and thereby produces a desired kind and degree of porosity in the finished compact.

Sintering.-The bonding of adjacent surfaces of particles in a mass of powder, or a compact, by heating. The terms core box and mold box have been used throughout the description and claims. is not limited to the specific application stated and is applicable to pattern boxes and vany arrangements wherein anenclosure is provided to contain a cavity for producing molds.

Thus it is believed that an improved process and article of manufacture has been described which will completely and eflicicntly accomplish the desired objects of the invention. It must be realized that changes and modifications may be made which do not depart from the spirit of the invention as. defined in the appended claims:

What is claimed is:

l. A. pressure molding assembly comprising a pair of separable moldv members having opposed parting faces, at least one of said mold members including a cavity in its parting face and defining in an assembled position with the facesin adjacent relation a molding chamber, asource of mold material under pressure, said chamber being adapted to be'placed into communication with said source of moldmaterial under pressure, each of said mold members beingconstructed of a sintered powdered metal having agenerally porous structure to provide permeability,

said powdered metal mold members also having copper 7 2. A molding assembly comprising a pair of separable moldmembers having opposed parting faces, at least one of said moldv members including a cavity in its parting facev and, defining in an assembled position with the faces in adjacent relation a molding chamber, a source of mold material under pressure, said chamber being" adapted to beplaced. into. communication with said source of'mold material, each of said mold members being constructed.

of a sintered powdered metal having a generally porous structure to provide permeability, said powdered metal mold members also havinghigh electricalresistivity, and

an electrical connector connected to each mold member and/being adapted duringconnection with an electrical source to pass a current through saidmold members therebyv heating the same whereby mold material within said cavity is heated and'cured, and gases incident to said curing are released through said porous mold members.

3. A molding assembly comprising a pair or separable mold mernbers having opposed parting faces, at least one of said mold members including a cavity in its parting face anddefining in an assembled position with the faces in adjacent relation a molding chamber, a source of mold material under pressure, said chamber being. adapted to be placed into communication with said source of mold material under pressure, each of said mold members being constructed of a sintered powdered metalhaving a generally porous structure to provide permeability, said The invention mold members having high electrical resistivity, and elec- References Cited in the file of this patent trical means connected to each mold member and being UNITED STATES PATENTS adapted during connection with an electrical source to pass 575,115 Hunt Jan. 12, 1897 a current through said mold mer nb ers thereby heatlng the 2,852,818 shauenberger et a1 Sept 23 1958 same whereby mold material wlthm said cavity 15 heated 5 1 and cured, and gases incident to said curing are released FOREIGN PATENTS through said porous mold members. 1 330,018 Great Britain June 5, 1930 

1. A PRESSURE MOLDING ASSEMBLY COMPRISING A PAIR OF SEPARABLE MOLD MEMBERS HAVING OPPOSED PARTING FACES, AT LEAST ONE OF SAID MOLD MEMBERS INCLUDING A CAVITY IN ITS PARTING FACE AND DEFINING IN AN ASSEMBLED POSITION WITH THE FACES IN ADJACENT RELATION A MOLDING CHAMBER, A SOURCE OF MOLD MATERIAL UNDER PRESSURE, SAID CHAMBER BEING ADAPTED TO BE PLACED INTO COMMUNICATION WITH SAID SOURCE OF MOLD MATERIAL UNDER PRESSURE, EACH OF SAID MOLD MEMBERS BEING CONSTRUCTED OF A SINTERED POWERED METAL HAVING A GENERALLY POROUS STRUCTURE TO PROVIDE PERMEABILITY, SAID POWDERED METAL MOLD MEMBERS ALSO HAVING COPPER METAL DISPERSED THROUGHOUT SAID POROUS STRUCTURE, SAID MOLD MEMBERS HAVING A HIGH ELECTRICAL RESISTIVITY, AND AN ELECTRICAL CONNECTOR CONNECTED TO EACH MOLD MEMBER AND BEING ADAPTED DURING CONNECTION WITH AN ELECTRICAL SOURCE TO DIRECT CURRENT THROUGH SAID MOLD MEMBERS THEREBY HEATING THE SAME WHEREBY MOLD MATERIAL WITHIN SAID CAVITY IS HEATED AND CURED, AND GASES INCIDENT TO SAID CURING ARE RELEASED THROUGH SAID POROUS MOLD MEMBERS. 